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CAUSES OF DEGENERATION OF AMERICAN TROUTS IN AUSTRIA 

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By Johann Franke 

Director of the Fish-Culture Establishment at Stwlencc and Secretary of the 
Fishery Committee for the District of Krain 

Paper presented before the Fourth International Fishery Congress 
held at Washington. U. S. A., September 22 to 26, 1908 

BULLETIN OF THE BUREAU OF FISHERIES. ; : ; : i : \OL. XXVIII. P. 983-989 
Documeni No. 699 ::: f ::::::::::::::: : Issued April. 1910 



983 



APR 15 1910 

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-■77 
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CAUSES OF DEGENERATION OF AMERICAN TROUTS IN AUSTRIA. 

By JOHANN FRANKE, 
Director oj the Fish-Culture Establishment at Studcnec and Secretary of the Fishery Commission jor the 

Province of Krain. 

J» 

[Translated from tlie German.] 

I have had to do with the feeding of rainbow and brook trout in ponds and 
inclosures for seventeen years. I have, had experience with rainbow trout in 
clear running water for thirteen years, and much more thoroughly and in detail 
with brook trout for eight years. 

The two species are excellent as breeders, first class and far superior to the 
native trout {Salmo jario). They can consume an astonishing amount of food, 
their appetite is extraordinarily persistent, and they repay the voracious feeding 
by astoundingly rapid growth; they remain well, keep their beautiful vivid 
coloring, and yield excellent spawn, even "red eggs" when in the proper condi- 
tion and in surroundings suitable to salmonoids. The view that the degenera- 
tion of this fish, wherever it has occurred, is a result of natural tendencies and 
the qualities of our water, and that the degeneration was to be expected in the 
nature of things, I entirely repudiate, for I am convinced that the degeneration 
is the effect of artificial conditions unsuitable to salmonoids. 

The true reason for the degeneration of these fishes is in faulty methods on the 
part of the fish culturists. The brook trout especially has been greatly dis- 
credited in Vienna and in other places, being pronounced very weak, its llesh 
distasteful, etc. This may have been true, as it is being bred in a most irrespon- 
sible way, the fish being given all kinds of impossible food in order to produce it 
quickly and cheaply. There is great competition in the sale of spawn, small 
producers selling not directly to the users but to agents who advertise not only 
hundreds of thousands but even a million or two as being their own product. 
The producer does not obtain even 3 crowns (60 cents) per thousand in many 
cases. Much of this has already been published in German special papers 

985 



986 BULLETIN OF THE BUREAU OF FISHERIES. 

discussing the subject of degeneration, and man)- astonishing facts have been 
brought out. Good eggs are cheap even at 5 crowns (or $1), and a iDreeding 
estabhshment can be maintained properly and on a businesshke footing only 
when the eggs bring 10 crowns. At present the fishes are bred down into a 
wretched condition. The much desired eggs from America will degenerate in 
the same way if the method of breeding for reproduction is not henceforth differ- 
ent from that which has prevailed. 

The unfavorable conditions surrounding the American trouts in this country, 
brought to my knowledge through experience during the long period I have men- 
tioned, I have found to be due partly to inadequate insight into many essentials 
of fish culture, and partly also to things which could not be changed. I have 
been able, however, to acquaint myself with some of the phenomena of degenera- 
tion and their causes, and some of them I have successfully combated. 

I consider the principal causes of degeneration to be: 

1 . Unhealthy pond bottom, i. e., bottom on which ooze and remnants of food 
as well as excretions accumulate for months at a time. The slower the current 
and the longer required for the water to run off, the more dangerous grow the 
conditions even at a low temperature of from 10° to 1 3° centigrade. The planting 
of water cress on the bottom and the introduction of carps and perches is not suffi- 
cient by any means, as these fish do not wallow in the ooze at temperatures of 10° to 
13°. For example: A spring pond having an area of 140 square meters and a 
depth of from 60 to 100 centimeters was stocked about the end of August with 
1,500 rainbow trout of the same year, and disease appeared in January, 1897; 
it was impossible to drain the basin without lowering the level of the water in 
the principal pond and disturbing the entire establishment. The ooze was 
taken out by means of a strong pump and a rubber hose ; in some places it was 
black and bad smelling. The disease disappeared entirely a few days later. 
After this I succeeded in saving the one-year-old fishes in low-water ponds with 
weak currents by means of frequent pumping out of the ooze and by keeping the 
bottom clean. 

2. Substitutes for the natural food. Fresh flesh of fishes (I had only fresh- 
water fishes) mvist be considered as natural by the effect produced, even if it is 
cooked. I never succeeded in keeping the trout healthy for a long period when 
using substitutes (a mixture of fresh blood cooked with shrimp meal, or the 
spawn of sea fishes, or fish meal — Ideal brand — and flour as a binding material) 
without an abundant addition of fresh fish. Within two and at the latest within 
three months there were traces of change of color to a darker, dimmer hue with a 
bluish tinge, more noticeable in the many-colored brook than in the darker rain- 
bow trout. If they reached the blackish-hue stage they could not be saved. In 
such cases live natural food without any adulteration proved the best of remedies. 



DEGENERATION OF AMERICAN TROUTS IN AUSTRIA. 987 

Latest example from the current year: Spring pond of 90 square meters, good 
depth, and slow current of the water at a temperature of 10° C. ; there were in the 
middle of February 400 beautiful rainbows from a lot of the previous year, of 
which 950 had been taken out in apprehension of lack of water in winter and 
sent to other places in November. The suspicious looking bluish tinge was 
already awakening our anxiety ; there was danger in delay, but the best remedy 
was natural food. A broad flat pool with spring water flowing through it, all 
covered with vegetation and algae, had become free of ice. Here were caught by 
means of a fine dip net a mass of various small animal life, small and large larvae 
of mosquitoes, crawfish, woodlice, small fishes, and even bullheads. The small 
animal forms came slowly to the surface from the thick forest of vegetation and 
dirt and were caught up. The entire mixture was then taken to the shallow 
water near the bank of the pond, where the trout themselves took the food out 
of this mixture. The pool supplied ample food year after year, thus saving the 
fishes more than once, though diminishing in abundance each year toward the 
month of May. Seven of these rainbows died, but all the remaining seemed 
well and acquired within three months their normal aspect, which they kept. 
To be sure, they were given no more food substitutes. The last 75 fishes were 
sent away in July; they weighed each 13 kilograms and stood very well the 
transportation of 6J2 hours, as did also those which were sent away earlier. 

As long as the materials for the diet of the small fry and young fishes con- 
tained crustaceans and fresh fish, the breeding and rearing went on exceedingly 
well, but in winter, with the forced use of substitutes, or in proportion to the 
lack of fresh fishes, the trouble began. 

3. Insufticient flow of water through the ponds. The two large ponds have 
an old accumulation of ooze at the bottom some 20 to 100 centimeters deep; 
can be emptied only down to five-sixths of their contents at best, as the entire 
system of springs of the establishment flows through these. This, which it is im- 
possible to correct, is surely an evil, but it had no apparent bad elTect upon 
the larger salmonoids and the breeding fishes so long as the flow was abundant. 
When the supply grew less, in 1897-98, there appeared again the exophthalmia 
and the "staggers" now and then. With the decrease of springs these phe- 
nomena grew more frequent, several of the native trout {fario) became miser- 
ably thin, and several rainbow trout yielded spawn that could not be used. In 
1904 the establishment went through two or three months without the flow of 
the springs, and in summer the surface water of the principal ponds at a certain 
distance from the inflow of the water had a temperature of 18° and near the 
exit a temperature of 21.2° C. At that time the water was calm, for what cur- 
rent could be expected from a couple of second liters in an area of 1^4 hectares? 
The water near the bottom was cooler by some 2° to 4°, and the trout lay there 



988 BULLETIN OF THE BUREAU OF FISHERIES. 

in lethargy and without appetite; only the roaches and a few carp swam 
slowly about. Good spawn was obtained only in ponds where there was an 
outflow of springs; there were but few brood fish in the places where formerly 
could be found some too kilograms; and good roe fishes were in still smaller 
number. In addition to this symptom of degeneration there were others in 
an increased degree. Anaemia, however, did not appear in the rainbow or brook 
trout. 

No food substitute whatever was given to the fish in the principal pond, in 
order to forestall a beginning of degeneration. This, however, was without 
avail. The regulation of the course of the principal river of the country gradu- 
ally drained away the living water supply of the establishment; the springs 
coming from the great subterranean stream of the Laibach field went dry, and 
we were forced to abandon the locality in July of this year. 

It is impossible to demonstrate in a more striking way than this the neces- 
sity of a good flow of water, one of the three conditions — infected bottom of 
ponds, continuous use of substitute foods, and insufficient flow of water — which 
brings about phenomena of degeneration, the more rapidly and in so much the 
higher degree if two or all three causes are operating at the same time. 

And what about native trout ? I would ask only when and where has there 
been observed in this fish any greater power of resistance against the above- 
mentioned causes of degeneration ? It is not less sensitive than the brook trout 
and considerably more so than the rainbow. 

As to the American trouts in running streams I know of only one drawback 
to the rainbow, namely, that there is no reason to suppose that it will remain 
and make a constant abode in particular w^aters, or that it will immediately 
leave the abode of its youth; water seemingly of the same character was in 
reality quite difi'erent. In two cases the fry developed in four years into mature 
fishes. The lingering of the rainbow in certain waters has astonished us as 
often as its disappearance from the same localities. 

The brook trout shows more tendency to remain. In waters where food is 
abundant this fish surpasses even the rainbow in rapid growth. Contrary to 
the general opinion that it must have cool water, I saw this fish thrive one 
summer in water having a temperature of 1 8° to 20° C. In small creeks, poor 
in food, it scarcely thrives as well as the native fario. In the Stara Voda, which 
stream I had under my control from 1901 to 1908, it grew to be the principal 
fish after the first introduction as small fry, while only a few of the rainbow 
trout had remained there. The native fario, which was already there and did 
well, remained far behind the fontinalis in numbers and in rapiditv of growth. 
Only during the last two years, when the stream suffered, like the establishment 



DEGENERATION OF AMERICAN TROUTS IN AUSTRIA. 9S9 

of Studenec, from lack of water and of current, the faiio stood it better than 
the jontinalis and appeared in greater numbers than the latter. 

Up to the time when I began to control this stream I knew nothing about 
the possibilities of the brook trout. Introduced into the stream in March, 1901, 
as small fry which had not yet been fed, several fishes were caught by me in 
August weighing from 0.3 to 0.5 kilogram, while the largest weighed 0.65 kilo- 
gram; they were fat and round, beautifully tinted, and their flesh was exquisite. 
The spawn (spawning season from November 7 to December 15) proved good 
in the hatchery, although the eggs were smaller than those of older fishes. 
Three-year-old fishes weighed 0.75 kilogram. I never dared to let them grow 
older through fear of their being stolen. 

My regret over the drainage of this stream is greater than for the ruin of 
the fish-culture establishment. 



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